1. Field of the Invention
The present invention relates to a current restriction circuit of an inverter refrigerator, in particular to a current limit circuit of an inverter refrigerator which is capable of driving a compressor of a refrigerator stably by making current set in advance flow when excess current flows due to an outside factor by adjusting a PWM duty cycle of a pulse width modulation controlling a power element.
2. Description of the Prior Art
In general, an inverter refrigerator is a refrigerator which is capable of optimizing a cooling air discharge and power consumption quantity by improving defects of an ON-OFF type refrigerator turning on/off a compressor with a certain time interval.
The inverter refrigerator comprises a SMPS (Switching Mode Power Supply), switching elements connected to a brushless DC motor (hereinafter, it is referred to a BLDC motor), a gate drive for controlling the switching elements, a position/speed detector for detecting a position and speed of a rotator of the BLDC motor, and a momentary excess current protection circuit.
FIG. 1 is a construction profile illustrating an excess current protection channel of the conventional inverter refrigerator, it comprises a rectification unit 10 for outputting a rectified and smoothed DC power source by rectifying and smoothing a common AC power source inputted from outside, a SMPS 11 for being inputted the DC power rectified and smoothed from the rectification unit 10 and providing the power to each circuit unit inside of an apparatus, an inverter unit 13 for being inputted the DC power provided from the SMPS 11 in accordance with a certain control signal, converting it into three phase power, and outputting it, an excess current detecting unit 12 for detecting excess current generation due to load change from the SMPS 11, a BLDC motor 16 driven by the 3 phase AC power of the inverter unit 13, a position/speed detector 17 for detecting the position and speed of the rotator of the BLDC motor 16, a microcomputer 15 for controlling a pulse width modulation signal by comparing position/speed of the rotator outputted from a detecting signal of the position/speed detector 17 with a requested phase angle and phase difference, and generating a pulse width modulation signal by being inputted an excess current detecting signal from the excess current detecting unit 12, and a gate driving unit 14 for controlling ON/OFF of the inverter unit 13 in accordance with the pulse width modulation signal outputted from the microcomputer 15.
The operation of the excess current protecting circuit of the conventional inverter refrigerator will now be described.
First, when the common AC power source inputted from outside is inputted to the rectification unit 10, the rectification unit 10 outputs the rectified and smoothed DC power source to the SMPS 11. The SMPS 11 inputted the DC power source provides a power to the each circuit unit as a transformer having different winding ratio each other.
The inverter unit 13 inputted the DC power outputted from the SMPS 11 outputs three phase power to the BLDC motor 16 by being ON/OFF in accordance with a control signal outputted from the gate driving unit 14.
When the BLDC motor operates, the position/speed detector 17 detects the speed and position of the motor rotator, and applies it to the microcomputer 15.
The microcomputer 15 judges the position and speed of the rotator by using the position and speed detecting signal of the BLDC motor rotator outputted from the position/speed detector 17, compares the detected position and speed with the requested phase angle and phase difference, and applies a PWM (Pulse Width Modulation) signal according to it to the gate driving unit 14.
Herein, the SMPS 11 is constructed with a plurality of windings having different winding ratio each other, accordingly a short circuit occurs frequently due to mutual contact of the windings, and excess current is generated by the load change due to it. Herein, the excess current detecting unit 12 detects the excess current due to the load change of the SMPS 11, and applies the excess current detecting signal in accordance with it to the microcomputer 15.
And, the microcomputer 15 outputs a control signal for turning off all switching elements of the inverter 13 to the gate driving unit 14 in order to protect damage of the compressor due to the excess current. It will now be described in more detail with reference to accompanying drawings.
FIGS. 2axcx9c2c are waveform diagrams illustrating the operation of the conventional inverter refrigerator excess current protection circuit in the excess current generation. For example, as depicted in FIGS. 2a and 2b, when higher than 9A arm short DC peak voltage is generated, the microcomputer 15 outputs the pulse width modulation signal to the gate driving unit. And, as depicted in FIG. 2c, the gate driving unit 14 protects the compressor by outputting the control signal to the inverter unit 13 in order to make the BLDC motor 16 turn off for 2 seconds xcx9c7 minutes.
However, in the conventional technology, when the excess current is generated, because the compressor is OFF for a certain time (2xcx9c7 seconds), mobility of the compressor lowers. In addition, in order to prevent turning off of the compressor during the operation and reduce mobility defect, the DC peak voltage is set as a voltage level corresponding to a high current of the arm short type, for example 9A, accordingly the efficiency lowers due to damage of the power elements or demagnetization of the motor of the compressor.
The object of the present invention is to provide a current limit circuit of an inverter refrigerator which is capable of making limit current set in advance flow into a motor of a compressor when excess current is generated by adjusting a PWM duty cycle of a pulse width modulation controlling the operation of current elements.
In order to achieve the above-mentioned objects, the current limit circuit of the inverter refrigerator in accordance with the present invention comprises a power unit 102 for providing DC power source to a BLDC motor 16 by being inputted an AC power source, a current detecting unit 101 for detecting current flowed into the BLDC motor 16, a control unit 200 for outputting a current limit control signal by being inputted a current detecting signal outputted from the current detecting unit 101 and comparing the present detecting current level corresponding to the current detecting signal with the current limit level set in advance, and a gate driving unit 14 for controlling the operation of the power unit 102 in accordance with the current limit signal outputted from the control unit 200.
In order to achieve the above-mentioned objects, the present invention comprises a setting process for setting a current limit level flowed into the motor, a comparing process for comparing the set current limit level with the present detecting current level, and a control process for controlling the current limit level so as to be flowed into the motor when the detecting current level is higher than the set current limit level.